1. Field of the Invention
The invention relates to a spring, more particularly to a spring having a stroke along a longitudinal axis and in which permanent magnets are used.
The invention also relates to an assembly of a spring and a damper and to a vehicle having a wheel and a wheel suspension in which a spring according to the invention is integrated.
2. Description of the Prior Art
U.S. Pat. No. 5,584,364 describes a magnetic unit used as a shock absorber or load leveler for a vehicle and having a plurality of groups of permanent magnets arranged in a side-by side relationship.
EP-A-0 391 066 describes an integrated spring system comprising a conventional spring, a magnetic spring and a damper. The magnetic spring has an inner part and an outer part each provided with permanent magnets, whereby the direction of the fields of the inner and outer parts are opposite so that a negative spring stiffness is provided, which, in combination with the conventional spring provides a spring system with a non-linear spring characteristic. The spring stiffness is small around the neutral or aligned position and is large when the spring is compressed further.
In both U.S. Pat. No. '364 and EP'066 the repulsive force of two neighboring permanent magnets, which are oppositely oriented, is used for evoking a spring effect.